Tiger Woods, who won the AT&T National at Congressional Country Club in 2009, is one shot back of the lead heading into the final round today. Brendon de Jonge, a Zimbabwean who doesn’t have a win on the PGA Tour, has the lead at 7 under.

Despite holding a lead, oddsmakers don’t like de Jonge’s chances of winning the tournament. De Jonge is +647 to win the AT&T, the fourth favorite in the field. Woods, to no one’s surprise, is the favorite at +151. Bo Van Pelt, who is tied with Woods and one shot back of the lead, is +543. And Hunter Mahan, who is two shots back of the lead, is +600 to leapfrog the four players in front of him and take home the victory.

Now, there have already been 5 first-time winners on the PGA Tour this year including Marc Leishman’s win at the Travelers Championship just last week. So that bodes well for de Jonge. But let’s take a look at some data on how 54 hole leaders perform in the final round.

From 2009-2011, outright leaders after 54 holes won the tournament 44% of the time. But that includes 54 leaders who had any kind of lead; one shot, two shots, three shots, etc. So since de Jonge has a one shot lead, let’s isolate the sample to one shot leads.

Again, from 2009-2011, there were 46 tournament leaders heading into the final round of a PGA event with a one shot lead. And 18 of them won the event. That’s a 39% win rate. So, if you were to extrapolate from this sample size of 46 instances, you’d estimate that Brendon de Jonge has a 39% chance of winning the AT&T National. And since he’s +647 (which implies just a 13% chance of winning), you’d want to bet de Jonge all day and night.

But before you do, remember two things: first, a sample size of 46 instances isn’t all that big. Second, we don’t have data on how would-be first-time winners do with 54 hole leads so it could be that the 39% win rate of one shot leaders is inflated by how well previous PGA winners do when they own a 54 hole lead.

A more complete odds listing for final round action from 5Dimes: